Water Quality in Cleveland Bay. Frequently Asked Questions

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1 Water Quality in Cleveland Bay Frequently Asked Questions 1

2 NATURAL WATER QUALITY IN CLEVELAND BAY What is turbidity and how does it relate to water quality? Turbidity is caused by particles suspended or dissolved in water that scatter light making the water appear cloudy or murky. What contributes to natural turbidity in Cleveland Bay? Cleveland Bay is naturally shallow, with most of it having a depth of less than 10 metres of water. Because it is relatively shallow, wind and wave action stirs up the sea floor in the area, creating natural turbidity. Other causes of natural turbidity include: heavy rain, cyclones or other significant weather events where sand and fine sediments are washed into Cleveland Bay from rivers and creeks (flood plume) coastal drift (where particles travel from the Burdekin River up the coastline) stormwater runoff from urban areas natural erosion of beach areas How often is naturally Cleveland Bay turbid? Historical records show that natural turbidity from wind and wave action (re-suspension) occurs on average 220 days of the year for water depths up to 5 metres (Orpin et.al., 2004). How does water quality in Cleveland Bay and around Magnetic Island compare to other coastal locations? Water quality in Cleveland Bay is comparable with the water quality from the mouth of the Burdekin River along the coast toward Hinchinbrook Island. This is due to the natural, predominantly north westerly coastal current drift parallel to the coastline from the Burdekin River. Water quality at Bowen south of the Burdekin River mouth is less turbid. Sheltered bays containing fringing coral reefs around Magnetic Island are generally less turbid than Cleveland Bay itself. Magnetic Island Cape Cleveland Townsville Ocean Land Ayr Burdekin River Mouth Wind and wave action cause resuspension of sediments indicated by the turbid zone around the coastline 2

3 NATURAL WATER QUALITY IN CLEVELAND BAY Sediment discharged into Cleveland Bay from Ross River Wind and wave action make the waters of Cleveland Bay turbid on a windy day outside the Townsville Port *Photo taken from the east of Cleveland Bay facing the port and the city of Townsville 3

4 DREDGING Why does the Port of Townsville dredge? Port of Townsville is designated by the Queensland Government as one of four Priority Ports in Queensland. Port of Townsville is vital to the economic viability of the North Queensland region to facilitate the import and export of goods such as containers, general cargo, motor vehicles, cattle, agricultural products, cement, bitumen, sugar and mineral concentrates. It is also crucial to cruise tourism and is a strategically important Defence port for Northern Australia. Port of Townsville Limited (POTL) is required to maintain a safe shipping channel and access to the Port of Townsville and ensure an efficient port service for the region. The shipping channel and berths act as silt traps, capturing sediment that would otherwise continue to move around Cleveland Bay due to wind, waves, tides and currents. Over time the channels become too shallow for safe ship access. To keep the channel passable, Port of Townsville has facilitated maintenance dredging every year since 1883 to ensure safe shipping access. Why is dredging important? If dredging didn t happen ships would be prevented from accessing the port. This would mean no supplies (like fuel, oil, food, cement, container cargo, building materials etc.) could get through to North Queensland by ship, and minerals and agricultural produce from North Queensland could not get out to national and international markets. What is the difference between capital and maintenance dredging? Maintenance dredging removes sand and fine sediment etc. from channels, berths and harbours where it has collected through natural processes such as wind or wave action. It is undertaken to maintain existing port facilities to provide vessels with safe access. In general maintenance dredging removes unconsolidated or soft material. Capital dredging involves removing sections of the existing seabed to create new shipping channels or enlarge existing ones, as well as berth areas, swing basins and harbour areas. In general capital material is consolidated or stiff material. What is beneficial re-use of dredge material? Beneficial re-use of dredge material is using the dredge material for another purpose, for example land reclamation, beach nourishment etc. The beneficial re-use options vary depending on the type and volume of dredge material. The majority of Port of Townsville s lands have historically been reclaimed through beneficial reuse of dredge material. Reclamation of Port of Townsville lands The red circle shows the site of the Port Administration buildings. 4

5 MAINTENANCE DREDGING How is maintenance dredging done? Port of Townsville undertakes maintenance dredging using a range of techniques, however the vast majority of maintenance dredging is carried out using a trailing suction hopper dredge (TSHD) called the TSHD Brisbane. The TSHD Brisbane has a pump system that is lowered over the side of the dredge on trailing arms and sucks up a mixture of sediments and seawater (like a vacuum cleaner) into a hopper or hold of the dredge. When the hopper is full the dredge travels to the approved dredge material placement area, opens the hopper doors below the water level and releases the sediment. In the Ross River a cutter suction dredge is used and material is received on shore for reclamation purposes. Where does the Port of Townsville place its maintenance dredge material? Throughout the Port s history maintenance dredge material has been placed both on land and at sea. Since 1993 the designated ocean Dredge Material Placement Area is a 12km 2 area located between Magnetic Island and Cape Cleveland in the deeper water away from sensitive coral reefs and seagrass. It is located outside the Great Barrier Reef Marine Park. The selection of this offshore Dredge Material Placement Area was the subject of a comprehensive assessment in 1992/93. This assessment was based on research and monitoring undertaken in conjunction with the Great Barrier Reef Marine Park Authority, James Cook University and the Australian Institute of Marine Science in relation to seabed fauna, hydrodynamics and sedimentation. The current site and dimensions were chosen for its proximity to key dredge areas, distance from the sensitive environmental receptors (corals, seagrasses etc.), sediment type, depth past the 10-metre depth contour and location outside of the Great Barrier Reef Marine Park. Maintenance dredging may also be placed on land where the volumes, suitability of sediment types and capacity exists. Who monitors and enforces conditions of maintenance dredging? The maintenance dredging program is subject to several environmental approvals and conditions from a range of Commonwealth and Queensland Government agencies (the Regulators ). All material is assessed against the Department of Environment and Energy s National Assessment Guidelines for Dredging and all activities are undertaken under an approved Dredge Management Plan. The Regulators monitor and enforce the Port s compliance with the maintenance dredging permit conditions. A Technical Advisory Committee has oversight of compliance and dredge volumes as well as current and proposed research for maintenance dredging. What other controls are in place to reduce the impacts of maintenance dredging? The dredging vessel, TSHD Brisbane is equipped with state-of-the-art dredge automation control, navigation system and turbidity control system which minimise the environmental impact of maintenance dredging. In addition: Dredging operations are timed to avoid events such as coral spawning, turtle nesting and severe weather events. Turtle deflectors ensure that dredging does not harm turtles. Sediment characterisation is undertaken before dredging to ensure that the dredge material is uncontaminated. Modern navigation and monitoring systems ensure that dredging occurs only in locations and at depths approved by environmental regulators. Hydrographic surveys are undertaken to ensure that dredging only occurs exactly where it is required Crew are trained in their environmental responsibilities. A specially designed valve reduces turbidity generated by dredging. Water quality monitoring helps us to understand our turbidity impacts. 5

6 MAINTENANCE DREDGING How well understood are the impacts of maintenance dredging on Cleveland Bay and Magnetic Island? Cleveland Bay has been the subject of significant research by the port, consultants and a broad range of research organisations including James Cook University, Australian Institute of Marine Science and the Great Barrier Reef Marine Park Authority. Research undertaken by, or on behalf of POTL includes turbidity and light monitoring in proximity to seagrass and corals, numerical modelling, verification testing and plume monitoring. These assessments involve modelling of typical and worst-case maintenance dredging campaigns. They found that impacts from annual maintenance dredging under different periods and zones of impact are restricted to areas within and immediately adjacent to dredging and placement areas only. As an initiative of its Community Liaison Group, Port of Townsville has undertaken to provide real time data on water quality in Cleveland Bay and at key tourism snorkelling sites around Magnetic Island. In the future water quality monitoring buoys will be deployed which enable real-time water quality data to be made available to the public on a dashboard which will be located on Port of Townsville s website. Dredge Material Placement Area Magentic Island Channel Port of Townsville GBRMP Boundary Cape Cleveland City of Townsville Location of Dredge Material Placement Area 6

7 C AP ITAL D R EDGI NG How will capital dredging for the Channel Capacity Upgrade project be done? Most of the capital dredging for the Channel Capacity Upgrade project will be carried out using a mechanical dredge. A mechanical dredge is an excavator (like you would see on a land-based building site) which sits on top of a barge. The use of an excavator enables solid and compact material to be removed from the seabed and transported by barge. Who monitors and enforces conditions of capital dredging for the Channel Capacity Upgrade project? The Port Expansion Project (PEP) has been assessed and approved through an EIS process by both the State and Commonwealth Governments. The capital dredging for the Channel Capacity Upgrade Project (Stage 1 of PEP) is governed by permits and approvals from a range of Commonwealth and Queensland government agencies (the Regulators ). The Regulators have set conditions for the project, including CHAN NEL W requirement and approval of a range of environmental management plans, monitoring programs as well as an oversight and enforcement role relating to compliance with these conditions. An Independent Technical Advisory Committee will provide scientific oversight and set thresholds to safeguard environmental performance during the capital dredging. The Committee will have the ability to stop works if any unacceptable impacts are observed through the extensive and continuous monitoring programs that are put in place. Where does the Port of Townsville place its capital dredge material? Capital dredge material from the Channel Capacity Upgrade project will be placed on land in the newly formed Reclamation Area. This beneficial re-use of dredge material is in accordance with the Sustainable Ports Development Act 2015 and Australia s Reef 2050 commitments to UNESCO. No capital dredge material is placed at sea. OR K S RECLAMATI ON AR E A Beneficial re-use of capital dredge material from the Channel Capacity Upgrade project to be placed in the Port Reclamation Area 7 MORE INFORMATION community@townsvilleport.com.au